Composite edge for producing double or multiple pane insulation glass or solar modules

ABSTRACT

An edge seal for manufacturing two-pane or multi-pane insulating glass or solar modules having a primary sealant and a secondary sealant has the following overall composition:
         a) 30-60 wt. %, preferably 40-50 wt. %, olefinic polymers, Mn 400-600,000 D, preferably 5,000-300,000 D   b) 2-35 wt. %, preferably 5-25 wt. %, modified polymer   c) 5-40 wt. %, preferably 10-30 wt. %, fine-particle, inert fillers   d) 5-25 wt. %, preferably 10-15 wt. %, desiccants and water scavengers 0-3 wt. % aging resistors, in particular anti-oxidants or UV stabilizers.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/679,250, filed on Oct. 18, 2010, which is hereby incorporated in itsentirety herein by reference.

FIELD

This invention relates to an edge seal for manufacturing two-pane ormulti-pane insulating glass or solar modules, there being provided aprimary sealant and a secondary sealant.

The construction of insulating glass units comprising two-pane ormulti-pane glass is known. In addition to the glass panes, it isstandard practice to use sealants and/or adhesives, spacers anddesiccants for this purpose. Solar-module glazing (both photovoltaicsolar modules and solar modules for heating water) is assembled in thesame way, except that the two glass panes can be replaced partially orcompletely by sheet metal and/or plastic film.

The spacer consists primarily of metal (usually aluminum), is located inthe edge area of the glass panes and has the function of maintaining thetwo glass panes at the desired distance apart. A desiccant (e.g. amolecular sieve) is contained additionally within the hollow spacer inorder to keep the air or gas trapped between the panes dry. To enablethe desiccant to absorb moisture at all, the spacer is provided withsmall apertures (longitudinal perforation) on the side facing theinterpane space. This arrangement prevents moisture from condensing onthe inside of the glass panes at low ambient temperatures and impairingthe transparency of the insulating glass unit.

Between the sides of the spacer that face the glass panes and the innersurfaces of the glass panes, a seal based on polyisobutylene and/orbutyl rubber is provided. This seal is generally known as the primaryseal. The function of the primary seal is

-   -   a) during production of the insulating glass panes, to be a kind        of “assembly aid” while the glass panes are being joined to the        spacer, which has been pre-coated with primary sealant, in order        to hold the assembly together during the next production stages,        and    -   b) later, during the service life of the insulating glass unit,        to form a water-vapor barrier that prevents moisture from        penetrating from the exterior inwards into the interpane space,        and, if the insulating glass unit is filled with gas, to prevent        loss of this gas outwards from the interpane space.

As the outward-facing edge of the spacer is a few millimeters inside ofthe outside edges of the glass panes, a “channel” is formed into whichthe secondary sealant, as it is generally known, is injected. The mainpurpose of the secondary seal is to elastically bond the edge of theinsulating glass unit (glass panes and spacer) and also to form aseal—which is to some extent an additional seal—against water and watervapor from the outside and gas from the inside (interpane space). As arule, the secondary seal consists of room-temperature-curing, two-partsealants and/or adhesives based on polysulfide, polyurethane orsilicone. One-part systems, for example based on silicone, or a hot-meltbutyl adhesive applied while hot, are also possible.

The systems described above, however, also have certain disadvantages.During production of the insulating glass units, a large number ofmaterials have to be processed in a series of complicated andcost-intensive stages, some of which take place simultaneously.

As far as the thermal insulation properties of the edge seal areconcerned, metal spacers used there have the disadvantage of being goodheat conductors and thus having a negative influence on an insulatingglass pane's desirable low K-value, which, in the case of double- ormulti-pane insulating glass, has been improved substantially in recentyears by filling the interpane space with inert gas and using glasspanes coated with low-emission (low-E) layers.

Particularly as a consequence of the second disadvantage, increasingnumbers of insulating glass systems have become available recentlywhich, in place of aluminum as spacer, use

-   -   a) prefabricated stainless steel profiles (lower wall thickness        possible and hence reduced heat flow) or    -   b) prefabricated plastic profiles or    -   c) prefabricated thermoplastic profiles or    -   d) extrusion compound comprising thermoplastic materials        extruded directly onto one of the glass panes.

On account of the improved thermal insulation properties in the edgeseal, these systems are also known as “warm-edge systems”.

Examples of c) may be found in EP 517 067 A2, examples and applicationmachinery for d) in EP 714 964 A1, EP 176 388 A1 and EP 823 531 A2.

The DE 196 24 236 A1 describes a hot-melt adhesive composition forinsulating glass, containing a mixture of at least one reactive binderbased on silane-functional polyisobutylene, hydrogenated polybutadieneand/or poly-α-olefins, and a non-reactive binder from the groupcomprising the butyl rubbers, poly-α-olefins, diene polymers, polybuteneor styrene block copolymers, which composition may be used as 1- or2-part adhesive/sealant in the production of insulating glasses. Noseparate spacers comprising metal or plastic profiles are needed here,and no additional, secondary sealants.

The DE 198 21 355 A1 describes a sealing compound for use in theproduction of multi-pane insulating glass; the compound containssilane-modified butyl rubber and serves as spacer between the individualpanes of the multi-pane insulating glass. Here too, no secondary sealantis needed.

Particularly those spacers extruded directly onto one of the glass panesalso overcome the problems relating to the manufacturing process. As aresult, insulating glass panes can be made using an automated processwhich is much more flexible and more productive.

In the field of solar module manufacture, too, applying the spacerdirectly onto the module edges in this manner has proved to offer manyadvantages. Compared, for example, with the manual or semi-automaticfitting of pre-extruded butyl tapes, this solution brings not onlyoptical advantages but also productivity advantages; in addition, itmakes for a more reliable long-term barrier against water-vaporpenetration and gas leakage. The EP 1 615 272 A1 (or DE 10 2004 032 604A1) contains a description of an exemplary method and device forassembling solar modules.

The thermoplastic material used combines the function of the spacer withthat of the primary seal, as it is called. It also contains thedesiccant. The TPS system (TPS=thermoplastic spacer) is an example ofsuch a system.

With these systems, too, the outward-facing edge of the spacer is a fewmillimeters inside of the outer edges of the glass panes, and theremaining space is filled by the secondary seal, as it is called, whichbonds the units elastically.

Where silicone is used as the secondary sealant in combination with athermoplastic spacer such as the TPS system, it has been found thatinsulating glass units, including those filled with inert gas, can bemanufactured substantially more reliably and retain their gastightnessin the edge seal even after a large number of weathering cycles (EP 916801 A2). It is very difficult to obtain equally low gas-leakage rateswhen using metallic spacers combined with a standard primary seal and asilicone-based secondary seal.

Combined with polysulfide as secondary sealant, the TPS system has, overthe past ten years, proved to be completely unproblematic ininsulating-glass fenestration applications.

However, particularly in cases where silicone is used as secondarysealant, there is a disadvantage that can, in certain cases, manifestitself as an optical defect within the insulating glass units. Acombination of:

-   -   a) materials (e.g. weather seal, EPDM glazing profiles, etc.)        which, due to external influences, are not compatible with the        insulating-glass edge seal, and    -   b) construction errors in the glazing area of the insulating        glass units, caused by inadequate planning (poor        ventilation/drainage of the glass grooves), and    -   c) extreme exposure (particularly high temperatures at the        insulating glass pane and in the edge seal) due to the situation        of the installation can cause deformation or movement of the        thermoplastic spacer profile into the interpane space. This        phenomenon is also known in German as the “Girlanden” Effect.        Depending on the quality of the TPS sealant used        (formulation/production process), there are marked differences        in susceptibility to the external influences described under        points a) to c). Where silicone is used as secondary sealant,        the main reason may be assumed to be the lack of adhesion        between the TPS sealant and the secondary seal, and the        inadequate adhesion—based only on predominantly physical        interactions—of the TPS sealant to the glass. This bond may be        easily weakened to a greater or lesser extent by substances        migrating into the glass/TPS sealant interface.

Proposals for creating a connection of such kind between the TPS and thesilicone secondary seal as to achieve mechanical anchorage or africtional connection by way of a specially shaped cross-section for theextruded TPS profile (DE 102 04 174 A1) unfortunately cannot beimplemented due to the impossibility of obtaining a suitably shaped diefor extruding such a profile cross-section. Another problem with thisproposal that has not been solved is exactly how to join up thebeginning and the end of the spacer profile extruded onto the glasspane. For a normal rectangular cross-section, this has been describedand solved in the EP 823 531 A2. A further difficulty with this proposalis encountered while applying the secondary sealant and consists in howto completely fill the partially convex voids within the TPS strandwithout incorporating any air bubbles. All in all, therefore, thisproposal is one that cannot be implemented as such in an everydayproduction process, and accordingly does not establish the desiredobjective.

Attempts to achieve chemical adhesion between the TPS sealant and thesilicone sealant by selective addition of traditional, silane-basedadhesion promoters to one and/or both sealants also fail. To this end,it is necessary to use grades and quantities which unfortunately have anegative influence on other desired properties, for example the workingconsistency of the TPS sealant, or which later on cause fogging in theinsulating glass when the unit has been installed.

The object of the invention is thus to provide an edge seal which isfree of the disadvantages described and which, especially also underhigh stresses (external influences due to incompatible materials,extremely high temperatures and UV radiation), ensures permanentstability of the TPS edge seal and thereby reliably prevents anydeformation of movement of the thermoplastic spacer profile into theinterpane space.

This object is established by means of an edge seal characterized inthat the primary sealant contains a polymer modified with special groupsand has the following overall composition:

-   -   a) 30-60 wt. %, preferably 40 to 50 wt. %, olefinic polymers, Mn        400-600,000 D, preferably from 5,000 to 300,000 D    -   b) 2-35 wt. %, preferably 5-25 wt. %, modified polymer    -   c) 5-40 wt. %, preferably 10-30 wt. %, fine-particle, inert        fillers    -   d) 5-25 wt. %, preferably 10-15 wt. %, desiccants and water        scavengers    -   e) 0-3 wt. % aging resistors, in particular anti-oxidants or UV        stabilizers, and that the secondary sealant is a silicone-based        sealant.

Thanks to the share of reactive groups bound to part of the primarysealant's polymer composition, the sealing compound according to theinvention adheres markedly better to other materials, in particularglass, metals and plastic, than is the case with prior-art sealingcompounds. In the invention, aside from the purely physical interactionswhich form the basis for glass adhesion in the prior art, chemical bondsare formed by hydrolysis-condensation reactions between the modifiedpolymer constituents and the chemically active groups (—Z—OH) of thesubstrate surface.

Where silicone is used as secondary sealant, the two sealants also bondadditionally by way of cross-linking across the interface between thesealing compound and the silicone sealant during its curing. The TPSsealant and silicone secondary sealant thereby produce a seal which issubstantially more stable toward external influences (e.g. plasticizermigration from incompatible materials), even at high temperatures andunder exposure to alternating temperatures, so that any formation of“Girlande” is completely ruled out.

One embodiment of the invention consists in that the olefinic polymersare selected from the group comprising polyisobutylene, polybutene,butyl rubber (polyisobutylene-isoprene), styrene block copolymers,especially SBS, SIS, SEBS, SEPS, SIBS, SPIBS, also in modified form, andamorphous copolymers and/or terpolymers of α-olefins (APAO).

The scope of the invention provides for the modified polymer to beselected from the group comprising polyisobutylene, polybutene, butylrubber (polyisobutylene-isoprene), styrene block copolymers, especiallySBS, SIS, SEBS, SEPS, SIBS, SPIBS, also in modified form, and amorphouscopolymers and/or terpolymers of α-olefins (APAO), the polymer beingmodified with at least one group of formula (1) which is a terminalgroup or is distributed statistically within the chain

where -A- is

and R¹ and R² are the same or different and are an alkyl group having 1to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms or anaralkyl group having 7 to 20 carbon atoms,X is a hydroxyl group or a hydrolyzable group,a is 0, 1, 2 or 3 and b is 0, 1 or 2, the sum of a and b being greaterthan or equal to 1, and where n is a whole number between 0 and 18, m isa whole number between 0 and 4 and R³ is

It is also within the scope of the invention for the fillers to beselected from the group comprising ground and precipitated chalks,silicates, silicon oxides and carbon blacks.

In this connection, the invention also provides for the chalks to besurface-treated.

However, it is also possible to use non-surface-treated chalks.

The invention furthermore provides for the silicates to be selected fromthe group comprising talc, kaolin, mica, silicon oxides, silicas andcalcium or magnesium silicates.

It is also with the scope of the invention for the desiccants or waterscavengers to be selected from molecular sieves (zeolites) of types 3Ato 10A.

Of course, other substances that bond water chemically or physically mayalso be used.

It is possible to formulate the sealing compound either as a one-partsealing compound or as a two-part sealing compound. In the case of aone-part sealing compound, all the components are mixed together duringthe production process. In the case of a two-part sealing compound, theolefinic polymers (a) are mixed together with some of the fine-particleinert fillers (c) and the water-binding fillers (d) in one part, e.g.part A; a second part, part B, is manufactured from some of thefine-particle inert fillers together with some of the olefinic polymers(a) and/or the entire quantity of modified polymers (b) and the agingresistors (e). The two parts of the compound are then mixed togetherimmediately prior to application.

The invention also provides for the aging resistors to be selected fromthe group comprising sterically hindered phenols, thioethers, mercaptocompounds, phosphorus esters, benzotriazoles, benzophenones, HALS andantiozonants.

Last but not least, it is also within the scope of the invention to usethe inventive sealing compound for fabricating insulating glass forwindows, conservatories, structural and roof glazing, for glazing inland-bound vehicles, watercraft and aircraft, and for manufacturingsolar modules.

The invention is explained in detail below by reference to an embodimentand a comparative example.

COMPARATIVE EXAMPLE 1 Prior Art

Composition:

-   -   a) 50 wt. % PIB of MW 60,000    -   b) 20 wt. % Carbon black    -   c) 14 wt. % CaCO₃    -   d) 15 wt. % A3-type molecular sieve    -   e) 1 wt. % phenolic antioxidant

Embodiment 2 According to the Invention

Composition:

-   -   a) 42 wt. % PIB    -   b) 12 wt. % silane-modified APAO or PIB    -   c) 10 wt. % CaCO₃    -   d) 20 wt. % Carbon black    -   e) 15 wt. % A3-type molecular sieve    -   f) 1 wt. % phenolic antioxidant

The effect of the sealing compound of this invention compared to theprior art becomes evident from the following comparative test:

To one long edge in each case of test insulating-glass panes measuring500×350 mm and constructed as 4 mm float glass/16 mm interpane space/4mm float glass plus the edge seal consisting in the one instance of

-   -   1) the sealing compound of the comparative example 1 as        thermoplastic spacer and a conventional 2-part silicone as        secondary sealant, and in the other instance of    -   2) the sealing compound according to embodiment 2 of the        invention as thermoplastic spacer and the same conventional        2-part silicone as in 1) as secondary sealant,        an EPDM profile of the kind typically employed for glazing        applications and having a plasticizer content of about 20%        mineral oil is bonded using a one-part silicone sealant with a        high silicone-plasticizer content, said profile thus being        brought into direct contact with the edge-seal sealants. The        test panes prepared in this way were then exposed to a        weathering-cycle test (−20° C./+80° C. at 95-100% rel. humidity,        8 hours per cycle, 3 cycles per day).

After only about 4-5 weeks of the weathering-cycle test, test pane 1)showed deformation, i.e. movement, of the thermoplastic spacer profileinto the interpane space. This was caused by the incompatibilityreactions (plasticizer migration from the EPDM profile and the one-partsilicone sealant).

Test pane 2), by contrast, showed no impairment of the edge sealwhatsoever even after more than 50 weeks of the weathering-cycle test.

Similarly, the glass adhesion and the edge seal showed no recognizableimpairment whatsoever after more than 4,000 hours of irradiation with UVlamps (Osram Ultravitalux) and temperatures at the pane surfaces of upto 110° C.

An edge seal that can withstand stresses of this kind is thus suitablenot only for insulating-glass applications in particularly demandingsituations, e.g. frameless glazing in facades or roofs (known asstructural glazing), but also, for example, for the edge seal in solarmodules.

In addition to the first application of a strand of reactive butylcompound, it is also possible to apply a second strand of butyl beforethe solar module is pressed. This is a particularly useful solution incases where the electrical contacts of the photovoltaic cells containedin the module are made to pass through the edge seal to the outside.After the first strand has been applied, the contacts—usually in theform of thin tape—are channeled to the exterior and the second butylstrand is then extruded directly on top of the first one. The contactsare thereby embedded in the butyl compound, thus ensuring that in thefinished solar module, the contact lead-throughs across the edge seal tothe outside are gastight and impermeable to water vapor. Since thecontacts are usually in the form of non-insulated metal tapes, the edgeseal must not show any electrical conductivity, as this can cause faultcurrent or short circuits between the contacts. In the case of asilicone-based secondary seal, this is no problem, since siliconestypically show very high volume resistivities, mostly >10¹⁴ Ohm·cm, andthus fall within the category of electrical insulators. However, butylsealants with a high filler content of Carbon black—as in the case ofthe reactive butyl compound described here—have volume resistivities of<10⁶ Ohm·cm, meaning that the compound would be electrically conductive.Reducing the Carbon black content admittedly increases the volumeresistivity, but also brings many disadvantages. Aside from mechanicalreinforcement and viscosity regulation, the purpose of a high Carbonblack content in a butyl sealant is to make the mixture particularlystable toward high temperatures and UV irradiation. If the Carbon blackcontent were to be substantially reduced because of the volumeresistivity, this would no longer be the case and the butyl sealingcompound would no longer show the required long-term stability forapplications in the field of solar modules, i.e. for applicationsinvolving high temperatures and solar radiation. By using a specialCarbon black in place of the Carbon blacks generally used in butylsealants, however, it is possible to obtain a reactive butyl compoundthat has all the required properties. It transpired that by selecting anoxidatively post-treated Carbon black made by the furnace process andhaving a primary-particle size in the 50-60 nm range, a Carbon black hadbeen found which not only permitted filler contents of up to 20 wt. %for the reactive butyl compound, which are necessary for stabilization,mechanical reinforcement and viscosity regulation, but simultaneouslyresult in a volume resistivity of >10¹⁰ Ohm·cm, which is fully adequatefor the electrical insulating effect required of the reactive butylsealing compound.

A special Carbon black of this kind is used in the following embodiment.

Embodiment 3 According to the Invention

Composition:

-   -   a) 40 wt. % PIB    -   b) 10 wt. % silane-modified APAO or PIB    -   c) 20 wt. % CaCO₃    -   d) 17 wt. % special Carbon black    -   e) 12 wt. % A3-type molecular sieve    -   f) 1 wt. % phenolic antioxidant

The following is claimed:
 1. An edge seal for manufacturing two-pane ormulti-pane insulating glass or solar modules, the edge seal including aprimary sealant composition and a secondary sealant composition, whereinthe primary sealant composition comprises: a) a modified polymer withspecial reactive groups; b) olefinic polymers of Mn 400-600,000 D, orcombinations thereof included in an amount from about 32% to 60% byweight of the total primary sealant composition; c) at least onefine-particle inert filler included in an amount from about 10% to 40%by weight of the total primary sealant composition; wherein the at leastone fine-particle inert filler comprises a carbon black included in anamount from 5% to 20% by weight of the total primary sealantcomposition, wherein the carbon black is oxidatively post-treated by afurnace process and has a particle size ranging from 50 nm to 60 nmresulting in the primary sealant having a volume resistivity of >1010Ohm·cm; d) at least one of a desiccant and water scavenger included inan amount from 5% to 25% by weight of the total primary sealantcomposition; and e) at least one aging resistor including ananti-oxidant or UV stabilizer included in an amount from about 0.1% to3% by weight of the total primary sealant composition.
 2. The edge sealof claim 1, wherein the modified polymer with reactive groups isincluded in an amount from about 5% to 35% by weight of the totalprimary sealant composition.
 3. The edge seal of claim 2, wherein the atleast one filler further includes a fine particle filler selected fromthe group consisting of ground and precipitated chalks, silicates,silicon oxides and carbon blacks that are different from the oxidativelypost-treated carbon black.